prep-changelog

#!/usr/bin/env node

import { readFile, writeFile, rename } from 'node:fs/promises';
import process from 'node:process';

async function main() {
  const version = JSON.parse(await readFile('./package.json', { encoding: 'utf8' })).version;
  const changesFile = 'CHANGELOG.md';
  const changes = await readFile(changesFile, { encoding: 'utf8' });
  const unreleasedRx = /^## Unreleased\n/m;
  if (!changes.match(unreleasedRx)) {
    console.error("Unable to find Unreleased section!");
    process.exit(1);
  }
  if (changes.match(new RegExp(`^## ${version.replace('.', '\\.')} `, 'm'))) {
    console.error(`${version} section already exists!`);
    process.exit(1);
  }
  const date = new Date();
  const dateString = [date.getUTCFullYear(), date.getUTCMonth()+1, date.getUTCDate()].map(d => d.toString().padStart(2, '0')).join('-');
  const newChanges = changes.replace(/^## Unreleased\n/m, `## ${version} (${dateString})\n`);
  const newFile = `CHANGELOG.md.${process.pid}`;
  await writeFile(newFile, newChanges, { encoding: 'utf8' });
  await rename(newFile, changesFile);
}

main();